/**
 * Copyright (c) 2012-2017, www.tinygroup.org (luo_guo@icloud.com).
 * <p>
 * Licensed under the GPL, Version 3.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * <p>
 * http://www.gnu.org/licenses/gpl.html
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.tinygroup.weixinhttpclient3.cert;

import org.apache.commons.httpclient.ConnectTimeoutException;
import org.apache.commons.httpclient.params.HttpConnectionParams;
import org.apache.commons.httpclient.protocol.SecureProtocolSocketFactory;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.tinygroup.vfs.FileObject;

import javax.net.SocketFactory;
import javax.net.ssl.*;
import java.io.IOException;
import java.io.InputStream;
import java.net.*;
import java.security.*;
import java.security.cert.Certificate;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import java.util.Enumeration;

/**
 * <p>
 * AuthSSLProtocolSocketFactory can be used to validate the identity of the HTTPS
 * server against a list of trusted certificates and to authenticate to the HTTPS
 * server using a private key.
 * </p>
 * <p>
 * <p>
 * AuthSSLProtocolSocketFactory will enable server authentication when supplied with
 * a {@link KeyStore truststore} file containg one or several trusted certificates.
 * The client secure socket will reject the connection during the SSL session handshake
 * if the target HTTPS server attempts to authenticate itself with a non-trusted
 * certificate.
 * </p>
 * <p>
 * <p>
 * Use JDK keytool utility to import a trusted certificate and generate a truststore file:
 * <pre>
 *     keytool -import -alias "my server cert" -file server.crt -keystore my.truststore
 *    </pre>
 * </p>
 * <p>
 * <p>
 * AuthSSLProtocolSocketFactory will enable client authentication when supplied with
 * a {@link KeyStore keystore} file containg a private key/public certificate pair.
 * The client secure socket will use the private key to authenticate itself to the target
 * HTTPS server during the SSL session handshake if requested to do so by the server.
 * The target HTTPS server will in its turn verify the certificate presented by the client
 * in order to establish client's authenticity
 * </p>
 * <p>
 * <p>
 * Use the following sequence of actions to generate a keystore file
 * </p>
 * <ul>
 * <li>
 * <p>
 * Use JDK keytool utility to generate a new key
 * <pre>keytool -genkey -v -alias "my client key" -validity 365 -keystore my.keystore</pre>
 * For simplicity use the same password for the key as that of the keystore
 * </p>
 * </li>
 * <li>
 * <p>
 * Issue a certificate signing request (CSR)
 * <pre>keytool -certreq -alias "my client key" -file mycertreq.csr -keystore my.keystore</pre>
 * </p>
 * </li>
 * <li>
 * <p>
 * Send the certificate request to the trusted Certificate Authority for signature.
 * One may choose to act as her own CA and sign the certificate request using a PKI
 * tool, such as OpenSSL.
 * </p>
 * </li>
 * <li>
 * <p>
 * Import the trusted CA root certificate
 * <pre>keytool -import -alias "my trusted ca" -file caroot.crt -keystore my.keystore</pre>
 * </p>
 * </li>
 * <li>
 * <p>
 * Import the PKCS#7 file containg the complete certificate chain
 * <pre>keytool -import -alias "my client key" -file mycert.p7 -keystore my.keystore</pre>
 * </p>
 * </li>
 * <li>
 * <p>
 * Verify the content the resultant keystore file
 * <pre>keytool -list -v -keystore my.keystore</pre>
 * </p>
 * </li>
 * </ul>
 * <p>
 * Example of using custom protocol socket factory for a specific host:
 * <pre>
 *     Protocol authhttps = new Protocol("https",
 *          new AuthSSLProtocolSocketFactory(
 *              new URL("file:my.keystore"), "mypassword",
 *              new URL("file:my.truststore"), "mypassword"), 443);
 *
 *     HttpClient client = new HttpClient();
 *     client.getHostConfiguration().setHost("localhost", 443, authhttps);
 *     // use relative url only
 *     GetMethod httpget = new GetMethod("/");
 *     client.executeMethod(httpget);
 *     </pre>
 * </p>
 * <p>
 * Example of using custom protocol socket factory per default instead of the standard one:
 * <pre>
 *     Protocol authhttps = new Protocol("https",
 *          new AuthSSLProtocolSocketFactory(
 *              new URL("file:my.keystore"), "mypassword",
 *              new URL("file:my.truststore"), "mypassword"), 443);
 *     Protocol.registerProtocol("https", authhttps);
 *
 *     HttpClient client = new HttpClient();
 *     GetMethod httpget = new GetMethod("https://localhost/");
 *     client.executeMethod(httpget);
 *     </pre>
 * </p>
 *
 * @author <a href="mailto:oleg -at- ural.ru">Oleg Kalnichevski</a>
 *         <p>
 *         <p>
 *         DISCLAIMER: HttpClient developers DO NOT actively support this component.
 *         The component is provided as a reference material, which may be inappropriate
 *         for use without additional customization.
 *         </p>
 */

public class AuthSSLProtocolSocketFactory implements SecureProtocolSocketFactory {

    /**
     * Log object for this class.
     */
    private static final Log LOG = LogFactory.getLog(AuthSSLProtocolSocketFactory.class);

    private FileObject keystoreUrl = null;
    private String keystorePassword = null;
    private FileObject truststoreUrl = null;
    private String truststorePassword = null;
    private SSLContext sslcontext = null;

    /**
     * Constructor for AuthSSLProtocolSocketFactory. Either a keystore or truststore file
     * must be given. Otherwise SSL context initialization error will result.
     *
     * @param keystoreUrl        URL of the keystore file. May be <tt>null</tt> if HTTPS client
     *                           authentication is not to be used.
     * @param keystorePassword   Password to unlock the keystore. IMPORTANT: this implementation
     *                           assumes that the same password is used to protect the key and the keystore itself.
     * @param truststoreUrl      URL of the truststore file. May be <tt>null</tt> if HTTPS server
     *                           authentication is not to be used.
     * @param truststorePassword Password to unlock the truststore.
     */
    public AuthSSLProtocolSocketFactory(
            final FileObject keystoreUrl, final String keystorePassword,
            final FileObject truststoreUrl, final String truststorePassword) {
        super();
        this.keystoreUrl = keystoreUrl;
        this.keystorePassword = keystorePassword;
        this.truststoreUrl = truststoreUrl;
        this.truststorePassword = truststorePassword;
    }

    private static KeyStore createKeyStore(final URL url, final String password)
            throws KeyStoreException, NoSuchAlgorithmException, CertificateException, IOException {
        if (url == null) {
            throw new IllegalArgumentException("Keystore url may not be null");
        }
        LOG.debug("Initializing key store");
        KeyStore keystore = KeyStore.getInstance("PKCS12");
        InputStream is = null;
        try {
            is = url.openStream();
            keystore.load(is, password != null ? password.toCharArray() : null);
        } finally {
            if (is != null) is.close();
        }
        return keystore;
    }

    private static KeyManager[] createKeyManagers(final KeyStore keystore, final String password)
            throws KeyStoreException, NoSuchAlgorithmException, UnrecoverableKeyException {
        if (keystore == null) {
            throw new IllegalArgumentException("Keystore may not be null");
        }
        LOG.debug("Initializing key manager");
        KeyManagerFactory kmfactory = KeyManagerFactory.getInstance(
                KeyManagerFactory.getDefaultAlgorithm());
        kmfactory.init(keystore, password != null ? password.toCharArray() : null);
        return kmfactory.getKeyManagers();
    }

    private static TrustManager[] createTrustManagers(final KeyStore keystore)
            throws KeyStoreException, NoSuchAlgorithmException {
        if (keystore == null) {
            throw new IllegalArgumentException("Keystore may not be null");
        }
        LOG.debug("Initializing trust manager");
        TrustManagerFactory tmfactory = TrustManagerFactory.getInstance(
                TrustManagerFactory.getDefaultAlgorithm());
        tmfactory.init(keystore);
        TrustManager[] trustmanagers = tmfactory.getTrustManagers();
        return trustmanagers;
    }

    private SSLContext createSSLContext() {
        try {
            KeyManager[] keymanagers = null;
            TrustManager[] trustmanagers = null;
            if (this.keystoreUrl != null) {
                KeyStore keystore = createKeyStore(this.keystoreUrl.getURL(), this.keystorePassword);
                if (LOG.isDebugEnabled()) {
                    Enumeration aliases = keystore.aliases();
                    while (aliases.hasMoreElements()) {
                        String alias = (String) aliases.nextElement();
                        Certificate[] certs = keystore.getCertificateChain(alias);
                        if (certs != null) {
                            LOG.debug("Certificate chain '" + alias + "':");
                            for (int c = 0; c < certs.length; c++) {
                                if (certs[c] instanceof X509Certificate) {
                                    X509Certificate cert = (X509Certificate) certs[c];
                                    LOG.debug(" Certificate " + (c + 1) + ":");
                                    LOG.debug("  Subject DN: " + cert.getSubjectDN());
                                    LOG.debug("  Signature Algorithm: " + cert.getSigAlgName());
                                    LOG.debug("  Valid from: " + cert.getNotBefore());
                                    LOG.debug("  Valid until: " + cert.getNotAfter());
                                    LOG.debug("  Issuer: " + cert.getIssuerDN());
                                }
                            }
                        }
                    }
                }
                keymanagers = createKeyManagers(keystore, this.keystorePassword);
            }
            if (this.truststoreUrl != null) {
                KeyStore keystore = createKeyStore(this.truststoreUrl.getURL(), this.truststorePassword);
                if (LOG.isDebugEnabled()) {
                    Enumeration aliases = keystore.aliases();
                    while (aliases.hasMoreElements()) {
                        String alias = (String) aliases.nextElement();
                        LOG.debug("Trusted certificate '" + alias + "':");
                        Certificate trustedcert = keystore.getCertificate(alias);
                        if (trustedcert != null && trustedcert instanceof X509Certificate) {
                            X509Certificate cert = (X509Certificate) trustedcert;
                            LOG.debug("  Subject DN: " + cert.getSubjectDN());
                            LOG.debug("  Signature Algorithm: " + cert.getSigAlgName());
                            LOG.debug("  Valid from: " + cert.getNotBefore());
                            LOG.debug("  Valid until: " + cert.getNotAfter());
                            LOG.debug("  Issuer: " + cert.getIssuerDN());
                        }
                    }
                }
                trustmanagers = createTrustManagers(keystore);
            }
            SSLContext sslcontext = SSLContext.getInstance("SSL");
            sslcontext.init(keymanagers, trustmanagers, null);
            return sslcontext;
        } catch (NoSuchAlgorithmException e) {
            LOG.error(e.getMessage(), e);
            throw new RuntimeException("Unsupported algorithm exception: " + e.getMessage());
        } catch (KeyStoreException e) {
            LOG.error(e.getMessage(), e);
            throw new RuntimeException("Keystore exception: " + e.getMessage());
        } catch (GeneralSecurityException e) {
            LOG.error(e.getMessage(), e);
            throw new RuntimeException("Key management exception: " + e.getMessage());
        } catch (IOException e) {
            LOG.error(e.getMessage(), e);
            throw new RuntimeException("I/O error reading keystore/truststore file: " + e.getMessage());
        }
    }

    private SSLContext getSSLContext() {
        if (this.sslcontext == null) {
            this.sslcontext = createSSLContext();
        }
        return this.sslcontext;
    }

    /**
     * Attempts to get a new socket connection to the given host within the given time limit.
     * <p>
     * To circumvent the limitations of older JREs that do not support connect timeout a
     * controller thread is executed. The controller thread attempts to create a new socket
     * within the given limit of time. If socket constructor does not return until the
     * timeout expires, the controller terminates and throws an {@link ConnectTimeoutException}
     * </p>
     *
     * @param host       the host name/IP
     * @param port       the port on the host
     * @param clientHost the local host name/IP to bind the socket to
     * @param clientPort the port on the local machine
     * @param params     {@link HttpConnectionParams Http connection parameters}
     * @return Socket a new socket
     * @throws IOException          if an I/O error occurs while creating the socket
     * @throws UnknownHostException if the IP address of the host cannot be
     *                              determined
     */
    public Socket createSocket(
            final String host,
            final int port,
            final InetAddress localAddress,
            final int localPort,
            final HttpConnectionParams params
    ) throws IOException, UnknownHostException, ConnectTimeoutException {
        if (params == null) {
            throw new IllegalArgumentException("Parameters may not be null");
        }
        int timeout = params.getConnectionTimeout();
        SocketFactory socketfactory = getSSLContext().getSocketFactory();
        if (timeout == 0) {
            return socketfactory.createSocket(host, port, localAddress, localPort);
        } else {
            Socket socket = socketfactory.createSocket();
            SocketAddress localaddr = new InetSocketAddress(localAddress, localPort);
            SocketAddress remoteaddr = new InetSocketAddress(host, port);
            socket.bind(localaddr);
            socket.connect(remoteaddr, timeout);
            return socket;
        }
    }

    /**
     * @see SecureProtocolSocketFactory#createSocket(java.lang.String, int, java.net.InetAddress, int)
     */
    public Socket createSocket(
            String host,
            int port,
            InetAddress clientHost,
            int clientPort)
            throws IOException, UnknownHostException {
        return getSSLContext().getSocketFactory().createSocket(
                host,
                port,
                clientHost,
                clientPort
        );
    }

    /**
     * @see SecureProtocolSocketFactory#createSocket(java.lang.String, int)
     */
    public Socket createSocket(String host, int port)
            throws IOException, UnknownHostException {
        return getSSLContext().getSocketFactory().createSocket(
                host,
                port
        );
    }

    /**
     * @see SecureProtocolSocketFactory#createSocket(java.net.Socket, java.lang.String, int, boolean)
     */
    public Socket createSocket(
            Socket socket,
            String host,
            int port,
            boolean autoClose)
            throws IOException, UnknownHostException {
        return getSSLContext().getSocketFactory().createSocket(
                socket,
                host,
                port,
                autoClose
        );
    }
}